Abstract

The celestite ore of Jebel Doghra occurs as stratabound deposits within the cap-rock of a diapiric structure of Triassic salt-rocks. The celestite deposits result mainly from the late diagenetic to epigenetic replacement of the carbonated host-rocks giving rise to a dolomite-celestite “banded ore”. Celestite is locally observed within fractures. This study proposes a new genetic model based on fluid inclusion (FI) microthermometry and REE geochemistry. FI show that celestite, occurring either as stratabound bodies or lodes, was deposited from a highly saline (20.7 ± 1.3 wt%NaCl equivalents) and warm (174 ± 3oC) basinal fluid, which contains hydrocarbon droplets and CO2. The geochemistry of the REE shows that the deposition of celestite is due to the mixing between a deep-sourced fluid which has acquired high Sr concentrations by leaching feldspar-rich series in depth and a sulfate-rich solution associated with the Triassic evaporites.

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